1. Field of the Invention
The present invention generally relates to photography and image capturing and, more particularly, to an image capturing apparatus, method, and computer readable medium utilizing customizable look management.
2. Description of the Related Art
Photographers generally sell their work based on their ability to impart an artistic look to a photographic image. This is generally done by a careful arrangement of the scene, including lighting, makeup, and other physical aspects, followed by the use of software tools, such as Adobe® PhotoShop®. The artistic look can take many forms but often it affects the colors in the picture. A professional photographer is very careful to protect his ‘look’ because that look is the reason that they are chosen by a client over another photographer with a different look.
Professional photographers working in a studio or on the fashion runway will often take many shots under very similar lighting. The setup for a ‘shoot’ can be very time consuming. If a problem arises during the processing of the photographs after the ‘shoot’ it may be very expensive or even impossible to reproduce the conditions and valuable time and money will be lost.
Photographers typically capture their images in a raw (unprocessed format) and then apply one or more proprietary color transformations to the colors in the images to attain their characteristic ‘look’. Before digital photography, these artists operated using film. Because of the limitations of the film medium, their output was limited to several dozen photographs and so the time required to process all individual images in a ‘shoot’ was relatively manageable. With digital cameras capable of taking hundreds of photographs in a ‘shoot’, customers of these artists have been demanding more images and, as a result, the time required to apply the ‘look’ has gone up. These artists desire a means to apply their ‘look’ to large numbers of digital photographs almost automatically.
Photographers can perform motion picture photography with cameras where sequential images are captured with varying time durations between each image. Motion picture photography is different from still photography in many ways. However, there are some similarities as well. Specifically, in both applications, artistic look needs to be introduced.
In the motion picture industry, look management is often achieved using color look-up tables (LUTs). Several digital motion picture cameras allow for the installation of LUTs. LUTs allow for the application of a look to the captured picture. LUTs normally convert film-centric RGB (Red-Green-Blue) values to revised film-centric RGB values and do not take advantage of color appearance or the human visual system.
Image capturing apparatuses, such as digital cameras, capture images and store them into a memory in one of two forms. High-end cameras can store the images in a raw (unrendered) form, which performs minimal processing on the images. This form is not viewable directly on an LCD (liquid crystal display) panel of the camera, nor can it be printed out directly. The second form, which is available on all cameras, is a rendered form. In this case, the colors in the image are converted to corresponding colors in a working color space, such as sRGB, AdobeRGB, or ProPhotoRGB. Very few digital motion picture cameras provide for raw, unrendered output; instead, they produce pictures that are rendered to one of several film standards color spaces, that is, they try to simulate the production of a motion picture on film.
In a rendered form, the images are usually processed to generate a set of colors that can be viewed on the LCD panel. However, the color capabilities of the LCD panel may not match the color capabilities of a final output device such as a printer. Because the camera is able to capture colors that are not available in the rendered output color space, during the rendering process these colors must be ‘gamut mapped’ to make them conform to the color range limits (gamut) of the output-referred color space to which the images are rendered. Ordinarily, the output referred-color space is a standard RGB color space, such as sRGB, Adobe RGB, or ProPhoto RGB. Because gamut mapping changes the image and because the changes are performed by the digital camera itself outside the control of the photographer, professional photographers usually prefer to use the camera in raw, unrendered mode so that they can control the rendering themselves.
In addition, if the final result of the images is to be printed, the rendering process needs to take into account the color capabilities (gamut) of the final output printer. Because the camera is generally not aware of the gamut of the final output printer, the image displayed on the LCD screen may not be a good depiction of the final result.
Rendering of color information is performed using a color management system (CMS). A color management system is a software system that is used to convert colors from one color space to another. This involves conversion of colors from an input device color space, gamut mapping from the color gamut of the input device and the output device, and conversion to the color space of the output device. A digital camera generally uses an internal color management system to perform this work when the images are rendered. This internal color management system is optimized for use with the digital camera as the input, a preset gamut mapping method, and a limited set of output color spaces, such as sRGB or AdobeRGB.
There are a number of different color management system architectures. Some color management systems, such as those used in imaging devices such as cameras and printers, use a very simple architecture that performs very simple rendering from one color system to another. Often, this is done using LUTs. More sophisticated color management systems, however, perform multiple steps in the rendering process with an aim at achieving superior results. These architectures generally make use of an intermediate, device-independent, color space.
The “Windows Color System” provided by Microsoft Windows® Vista and the Canon Kyuanos system change colors in several distinct steps. First, the colors in the image are converted to a colorimetric representation, that is, they are converted to CIEXYZ as defined by the Commission Internationale de l'Eclairage (CIE) as a mathematical color space that describes color in terms of synthetic primaries X, Y and Z. The primaries are imaginary mathematical constructs that model responses of the human eye to different wavelengths of light. This is a device independent form of color representation that models the human visual system.
The second step is converting the CIEXYZ representation to a color appearance representation in the color appearance space called CIECAM02, which transforms physical measurements of the color stimulus and viewing environment into relative perceptual attributes including lightness, chroma and hue. This color representation provides a model of color that is ‘linear’ with respect to human perception. While the image is encoded in CIECAM02, gamut mapping is performed. Gamut mapping is performed in color appearance space because it is easier due to the linearity of the space. Gamut mapping involves the use of algorithms which convert the coordinates of color values of one color space into another. Then the gamut mapped image is converted back to CIEXYZ and finally the results are converted to RGB in the desired rendering color space.
The use of computer based tools for applying artistic look has a disadvantage. While computer based tools, such as Adobe® Photoshop®, are available to apply custom artistic transforms to a batch of images, the tools operate in a computer and must be used after a photography shoot is completed. Currently, there is not a good way to apply these look operations at the time photographs are being taken so as to ‘preview’ the images when it is still possible to retake a shot.
In professional digital photography, there is a need for a way to apply an artistic look to a series of images in such a manner that the look can be used with different cameras and the results of the use of the look, as they would appear on the final output device, can be previewed by the photographer at the time the photographs are taken so that changes in either look or studio setup can be performed right away, while the models and studio are at hand. To satisfy this need, we propose image capturing systems and methods utilizing customizable look management provided by the photographer.